v0.21 released

This version provides some much needed bug fixing and new features. The biggest feature added in v0.21 is the ability to nest components in containers, including other containers. A component may be moved to a container by dragging it with the left mouse click onto a container. The container that the component will be dropped onto is highlighted in green, and the selected component is highlighted red.

I've also moved all of the controls into a toolbar, and made the app window resize so that it's not a fixed width, making it more usable on large and small displays.

I've changed the output of the .wdf files to be XML based instead of the more cryptic format, which should make it easier to interoperate with these data files.

Finally, I've updated the look and feel of the components a bit to make them a little nicer looking.

I'd really like some feedback from anyone who downloads this release. I've noticed a few hundred people have downloaded this app over the last couple of years and haven't heard anything back, positive or negative.